Agents imparting flame retardant properties have been developed for polyamide and polyester fibers, molding compounds, carpets and other polyamide and polyester materials. Such agents frequently include a halogen-containing ingredient, which may render the material unsuitable for certain applications because of smoke formation, toxicity of various types or various other properties. Among the most common flame retardant materials are antimony oxide and antimony chloride.
Metal salts of hydroxycarboxylic acids have been suggested for use as a component for flame retardant compositions in U.S. Pat. No. 3,956,236 of F. E. Evans et al. in combination with certain organic acids or their ammonium salts, particularly hydroxycarboxylic acids or their ammonium salts. Also, U.S. Pat. No. 3,943,100 to M. B. Berenbaum et al. describes flame retardants based on certain organic acids, e.g., gallic acid, citric acid, or tartaric acid, or the ammonium, lithium or magnesium salts thereof. Although these patents constitute a major contribution to this art, investigations have been continued to develop improved flame-retardant fibers and molding compounds.